1. Field of the Invention
This invention relates to grinding machines.
2. Introduction to the Invention
U.S. Pat. No. 1,928,390 discloses a grinding machine comprising a frame having a rotary casing that bears rotary holders for grinding discs, as well as a drive motor which is mounted on the frame and interacts with the casing and the holders to drive the machine. In this machine, a drive shaft is connected to the drive motor via a gear transmission and to the casing, which can thus be brought into rotation; and the holders for the grinding discs are brought into rotation via a V-belt, which is fed around a stationary pulley on the frame, and pulleys on the shafts of the holders.
A drive system of this type has various disadvantages. For instance, it is not easy to change the relative speeds of rotation of casing and holders with respect to one another, nor is it easy to change their relative direction of rotation. Because the drive shaft is connected directly to the casing, a reduction unit has to be incorporated between drive motor and said drive shaft, since otherwise the casing would rotate too rapidly.